Control of camera-subject motion in motion-picture photography



AU@ 1l, 1953 G. L. sTANcLlFF, JR.. ETAL 2,548,252

CONTROL OF CAMERA-SUBJECT MOTION IN MOTION-PICTURE PHOTOGRAPHY Filed Sept. 17, 1948 8 Sheets-Sheet l L-J Genera/'or' k@ fel a 5&1 Q y 55E /Qg .56

Aug. 11, 1953 G. l.. sTANcLlFF, JR.. ETAL 2,648,252

CONTROL OF CAMERA-SUBJECT MOTION IN MOTION-PICTURE PHOTOGRAPHY 8 Sheets-Sheet 2 Filed Sept. 17, 1948 Aug 11 1953 G. L. sTANcLlFF, JR., ETAL 2,648,252

CONTROL OF' CAMERA-SUBJECT MOTION IN MOTION-PICTURE PHOTOGRAPHY 8 Sheets-Sheet 4 Filed Sept. 17, 1948 Aug 11, 1953 G. L. sTANcLlFF, JR.. l-:TAL 2,648,252'v CONTROL OF' CAMERA-SUBJECT MOTION IN MOTION-PIOTURE PHOTOGRAPHY Aug- 11, 1953 G. l.. s'rANcLlFF, JR., Erm. 2,648,252

CONTROL OF CAMERA-SUBJECT MOTION IN AMOTION-PICTURE PHOTOGRAPHY 8 Sheets-Sheet 6 Filed Sept. 17, 1948 [Ill Aug. ll, 1953 G. L. s'rANcLlFF, JR.. r-:TAL 2,648,252

` CONTROL OF CAMERA-SUBJECT MOTION IN MOTION-`PICTURE PHOTOGRAPHY Filed sept. 1v, 194e a sheetsneet 7 Aug. ll, 1953 G. L. sTANcLlFF, JR.. ETAL 2,648,252

CONTROL OF CAMERA-SUBJECT MOTION 1N MOTION-PICTURE PHOTOGRAPHY Filed Sept. 1'?. 1948 8 Sheets-Sheet 8 366 j jjj@ l 54a 549 74 Jv vez? 710.275

-izzyz 4l'atented ug. v11, 1953 CONTROL OF CAMERA-SUBJ ECT MOTION IN MOTION -PICTURE PHOTOGRAPHY Gilbert L. Stancli", Jr., Burbank, and Henry Gordon Jennings, Los Angeles, Calif., assignors, by mesne assignments, to Paramount Pictures Corporation, a corporation of New York Application September 17, 1948, Serial No. 49,756

1 Claim.

This invention is concerned generally with methods and apparatus for taking motion pictures in which there is relative motion between the camera and the subject as a whole. The invention relates more particularly to procedures wherein various portions of such relatively moving subjects are photographed separately and combined photographically by any of the usual methods of composite photography.

An important purpose of the invention is to provide means by which the relative position and orientation of camera and subject can be varied automatically through a predetermined pattern of motion. Thus a selected pattern of motion can be repeated by setting the control system for the desired pattern and allowing the pattern to be automatically produced repeatedly.

The invention further permits an arbitrary pattern of relative motion to be recorded in convenient and durable form, and to be repeated at any later time. The original motion pattern may be produced by the automatic controls just referred to, or may be a completely arbitrary motion such as results, for example, from manual operation of the usual camera hand wheels. In either instance, when the motion is repeated, that repetition may be made so accurate that the ordinary procedures of composite photography are applicable. Thus the invention has the important result of opening up virtually a new v'i'leld for composite photography, namely that in which there is relative movement of an arbitrary kind between the camera and the subject as a whole.

The most satisfactory type of apparatus for .carrying out the invention depends upon the :type of motion picture sequence that is to be photographed. Under some conditions the use- ;fulness of repeating the relative motion of camera and subject requires an extreme degree of accuracy, say, within a few minutes of arc, equaling or at least approximating the limit of resolution of the photographic process itself. That is generally true, for example, in photographing successively separate color components of a subject which are subsequently assembled as a composite; or in photographing successively different portions of a subject which must match in detail in the final composite print. In other instances, a less accurate repetition of the relative motion, say within a quarter of a degree or more, is sufficient, as when a cloud background is to be introduced into a landscape sequence involving camera motion.

The invention is useful also under many conditions not involving composite photography. For example, when a scene involving a relatively complex program of camera motion must be retaken several times, the automatic repetition of that motion, even with moderate accuracy, may give more uniformity than can be obtained manually, and avoids the possibility of error in following the set program. It may be important in repeated motion to obtain great accuracy in the time at which variations of motion occur, as, for example, in a dance sequence in which camera motion must be synchronized with music already recorded. A sequence requiring such time accuracy may or may not require similar accuracy in the space coordinates of the motion.

When the required relative motion of camera and subject takes place in several distinct coordinates, each of those coordinates is preferably treated independently, both as to the means for producing and controlling the initial motion and as to the means for recording and repeating the motion. Thus one unit or channel of the recording-repeating mechanism is preferably provided for each component of motion. The various channels may be closely associated physically, as by employing common power sources, mechanical supports and housings, etc., but they preferably are capable of functioning independently of each other. Interactions of various types between the different channels may be introduced as required, but for most purposes it is suiiicient to provide an accurate correlation between the time scales of the different channels, so that the time relations between motion in the corresponding coordinates will be correctly reproduced. Such a time correlation is ordinarily provided by starting the recording channels in unison and operating them at the same speed or at definitely related speeds.

The actual record of the camera-subject motion in any one coordinate is made, according to a preferred embodiment of the invention, by scribing a line lengthwise of a moving record strip or tape, the transverse position of the line on the strip corresponding at every instant to the momentary value of the coordinate. The record tape is preferably drawn longitudinally at uniform speed over a surface, which may be xed, or may move with the tape, while a scribing tool is held in scribing relation to the tape and is so linked to the camera or subject that it moves transversely of the tape directly proportionally to the associated coordinate of camera-subject motion. To repeat the motion, the tape is drawn under a following tool which 3 follows the transverse motion of the record line, and which is so linked to the camera or subject as to reproduce proportionally the original motion.

The type of linkage used is preferably capable of giving high accuracy, and, particularly in the case of the repeating linkage, must exert a relatively great force o1` torque upon the driven element with a relatively small reaction force upon the controlling element. These requirements are met by using linkages of the servo type involvingT a closed control circuit between driven and control elements. One branch of that control circuit includes a source cf external power which acts under control of a differential device in the other branch of the circuit, and which drives the driven element in a manner directly corresponding to any arbitrary motion of the controlling element. Hence the reaction force on the latter is only that of the diiferential device, which can be made negligibly small. The nature of the correspondence between the motions of driven and controlling elements is determined primarily by the diiferential device, and can be varied greatly to suit requirements.

By suitable choice of the linkages used (that is, of the differential devices of the servo syrtems), the factors of proportionality between the camera-subject motion and the transverse motion of the scribing and repeating tools can be so adjusted as to compress the original camerasubject motion into the available tape width during recording; and to expand the motion cf the` repeating tool correspondingly to give a repeated camera-subject motion of the desired scale. Ordinarily the repeated motion duplicates the original motion, but under certain conditions it is desirable to use a different factor of proportionality in the recording and repeating linkages, leading to repetition of the motion at a different scale, including the possibility of a different time scale. The invention also inclu-des the possibility of reproducing the original motion with a scale factor which is variable. For example, the scale factor at which a translational motion is reproduced may be varied in accordance with the value of a rotational coordinate.

A clear understanding of the invention, and of its further objects and advantages will be had from the following description of two illustrative mechanisms for obtaining relative motion between camera and subject, and a preferred form of apparatus for recording and repeating any such motion. It will be clear from that description how the invention may be carried out with respect to other types of motion, when greater or less accuracy of reproduction is needed, and under similarly varied conditions. It is not intended that the scope of the invention be limited by details of this illustrative description or of the accompanying drawings, but that scope is defined by the appended claims. In the drawings:

Fig. l is a functional diagram of a rudimentary system in accordance with the invention, for recording arbitrary camera motion in three dimensions and repeating that motion an indefinite number of times;

Fig. 2 is a fragmentary side elevation, partially broken away and somewhat simplified for clarity, showing a typical camera support in accordance with the invention;

Fig. 3 is an end elevation of the camera support of Fig. 2, partially broken away and similarly simplified;

Fig. 4 is a horizontal fragmentary section at enlarged scale, taken as indicated by lines 4-4 in Figs. 2 and 5;

Fig. 5 is a fragmentary vertical section taken as indicated by the lines 5-5 of Figs. 3 and 4, and at the scale of Fig. 4;

Fig. 6 is a side elevation of a typical dual channel recording-repeating mechanism in accordance with the invention;

Fig. 7 is an end elevation of the mechanism of Fig. 6, showing portions in section as indicated by the lines 'IA-IA and 'IB-'IB of Fig. 6;

Fig. 8 is a horizontal section at enlarged scale, taken on line 8-8 of Fig. 7;

Fig. 8A is a vertical section at enlarged scale, taken on line BA-SA of Fig. 8 showing the arm latch in locking position;

Fig. 9 is a fragmentary section on line 9 9 of Fig. 6;

Fig. l0 is a schematic diagram of a preferred electrical system for use with a camera support and recording-repeating mechanism such as are shown in Figs. 2-9;

Fig. ll is a schematic diagram of a preferred electrical system for use with a movable support such as that in Fig. 12;

Fig. l2 is a schematic elevation of a subject support adapted for providing controlled motion in three coordinates;

Fie. 13 is a schematic elevation, corresponding to the portion of Fig. l2 below the line i3, and illustrating the use of the movable support of Fig. l2 as a camera support; and

Fig. le is a schematic plan, illustrating a typical photographic procedure.

Fig. l is a functional diagram representing a camera support 22 having controllable motions in three coordinates, namely, tilt (swinging in a vertical plane), pan (swinging in a horizontal plane) -and dolly (translational movement along a line); and a recording repeating system comprising three channels associated respectively with those coordinates. Since the principle of operation of all three channels is the same, only the first will be described in detail.

The-tilt motion of cameraa@ on its support 22 is connected by any suitable linkage, indicated by the dashed line 25, to a shaft 25, which is positively connected directly or through gearing such as 2l with a reversible servomotor 23 and also with the rotor 24 of a synchro generator 29. The units just mentioned are ordinarily physically supported on camera mountv 22. The recordingrepeating unit proper, associated with the tilt motion, comprises means for supporting and uniformly driving a recording tape 3G, such means being indicated in Fig. 1 by the tape drum 3l and the synchronous A. C. motor 32, in driving relation to the drum; and a transversely swingable arm 34A adapted to carry at its end alternatively means for cutting or otherwise scribing a line 33` in tape 33, or means for following a line already carried by the tape. Arm 34 is shown extending radially from a shaft 35 which is connected directly to the rotor 38 of the synchro transformer 35, and is connected by the gear train 3l to the reversible servomctor 3.8.

The rotor 213 of synchro generator 29 is electrically connected via cable 4l (representing two conductors) through switch G3 to a source of alternating current of suitable frequency, and its stator coils are connected via cable 42 (representing three conductors) to the stator coils of synchro transformer 36. The rotor 39 of transformer 3E is thus subjected to an alternating magnetic neld, the direction f which depends upon the rotational position of the rotor of synchro generator 29; and the alternating signal voltage induced by that magnetic field in the transformer rotor 39 thus depends in magnitude and phase upon the relative rotational positions of the two rotors. In particular, if the rotors are so oriented as to produce zero signal voltage, their positions may be said to correspond. The tilt position of camera 20 and the transverse position of arm 34 with respect to tape 3|), being positively linked to the respective rotors 24 and 39, then similarly correspond. Thus a definite correspondence between camera tilt and arm position is dened by the succession of relative positions for which the signal produced from transformer 36 is zero. If the said correspondence does not obtain, an alternating current error signal is produced in the rotor 39 of synchro transformer 36, the amplitude and phase (with relation to the phase in line 4|) of the signal varying with `and indicating the magnitude and direction of the error. That signal is transmitted via cable 45 through double throw switch d6 to recording amplifier 41 if a camera motion is being recorded on tape 30, and to repeating amplifier 43 if a previously made record on tape 33 is being used to control the camera tilt. In the former instance, the error signal, after amplification and phase-sensitive rectification in recording amplifier 41 is supplied via line 49 to recording D. C. servomotor 33 as a D. C. potential of appropriate size and direction to drive arm 34 in such a direction as to reduce the error signal. With a suitably designed and constructed system, that action results in arm 34 following very accurately the tilt motion of the camera, in the sense of the definite correspondence described above. Thus the resulting record line 33 scribed on moving tape 3i) correctly represents the tilt motion of the camera as a function of time. While making such a record, the camera tilt can be manipulated in any convenient way, for example by the tilt hand wheel ordinarily provided on the camera mount and indicated schematically at 59, or by remote control means to be described.

When a sequence of tilt motion, previously recorded on tape 30, is to be repeated, the tape is moved by motor 32 under arm 34 at the same speed that was used for recording. Arm 34 is now provided with means for following the record line 33 in tape 39, and the arm is thereby constrained to swing with its shaft 35 in the same time sequence of motion which it followed while the record line was recorded. Recording servomotor 33 is preferably disconnected from shaft 35, to reduce the load imposed upon the record following means. If the position of the camera about its tilt axis does not correspond to the record-controlled position of arm 34, an error signal is generated in rotor 39 of synchro transformer 36 and is transmitted now through switch 4S in its repeat position to repeating amplifier 49. After amplication, rate anticipation and phase-sensitive rectification, the error signal is applied as a driving voltage of appropriate sign via cable 5| to repeating servomotor 23, which then alters the camera tilt in a direction to reduce the error. In practice that corrective action holds the error to a very small value at all times. Thus the camera tilt position at every instant of the repeat motion is substantially identical with that at the corresponding instant of the original motion. Power to drive the camera during the repeat motion comes primarily from amplifier 48, and the reaction of arm 34 upon the record line 33 which guides it is very small. Hence the record line may comprise, for example, a scribed line in a relatively soft material such as ordinary motion picture film. A record line a few thousandths of an inch deep in such material has been found to show no noticeable wear after as many as repeating runs.

As indicated in Fig. l, separate record strips 30h, 30o are used to record the pan motion and the dolly motion respectively, separate channels being provided for recording and reproducing the motion in each coordinate. Those channels, may be all identical in their principle of operation, and are so represented in Fig. 1, Where corresponding parts in the pan and dolly chan-v nels are denoted by the same numerals as in the tilt channel, but `with addition of suffixes -b and -c respectively. The description given above for operation of the tilt channel is also applicable to each of the other channels, if -lr or -c suffixes are added to the numerals and other obvious changes in terminology are made.

When all three channels are in operation the motion of the three record tapes 30, 30h and 33C must ordinarily be synchronized with each other. That can be done, for example, by mechanically linking together the three film drums 3|, 3| b and 3io. Alternatively, the tape drives may be mechanically independent, but linked electrically, as by use of synchronous interlock drive motors 32, 32h and 32c supplied with alternating current from the same source and under control of a single switch or its equivalent.

An important feature of the invention, as ordinarily carried out, is the synchronization of the tape drives in the various channels of the recording mechanism with the camera drive motor. The latter is indicated at 51, mechanically connected to the intermittent mechanism 63 by which film 64 is drawn through camera 20. With such synchronization, there is a definite relation between the longitudinal position of a particular frame on the motion picture film 64 and the longitudinal positions on the respective recording tapes 30 for which the records 33 correspond to the position of the camera at the time that frame was exposed. Typical driving means for synchronizing the camera and the recording-repeating drums 3| are indicated in Fig. l, and are generally similar to the usual interlock drive employed for synchronizing the camera and a sound recording system. The tape drive motors 32, 32h and 32C, as well as camera motor 51, are of self-synchronous, or selsyn type, driven from a selsyn generator 58, which is mechanically connected to a drive motor 59. The rotors of the selsyn motors and cf generator 58 are interconnected in parallel via cables S0, which represent the usual 3 wires of a S-phase system. Suitable 3- phase power is supplied from a source 6| via lines 54 to the stators of the selsyn motors 32, 32h, 32e and 51, and of generator 58. Individual switches 55, 55D, 55o and 55d are provided in lines 54 for the respective motors, and a master switch 53, inserted in power line 6l, controls the entire system. It is convenient to connect driving motor 59 to lines 54, as indicated, so that it is also under control of switch 53. Motor 59 is preferably of the slip ring synchronous type with its rotor windings shorted through 7 a variable resistance (not shown) to provide convenient speed control, including a definite synchronous speed.

Each of switches 53, 55, 55h, 55e and 55d in practice comprises two separately operable switches, closure of one of which applies single phase voltage to bring the rotor of theassociated motor into interlocked alinement with selsyn generator 58 before S-phase Yvoltage is applied 4by closing the second switch. For clarity of description the dual nature of those switches will generally not be explicitly noted.

In recording a sequence of camera motion, the three recording-repeating channels are rst energized by closing switch 63, providingpower over lines 4l, lib and Mc to theampliers and synchros. With switches k4G, 519 and 4Go in recording position (as in Fig. l), this brings each recording arm 3d into a position corresponding to the associated camera position. The tapes38,

30h and 3Go are threaded over their drums and the starting point on each tape is preferably marked for convenient reference.

Film 54 is provided in camera 20. Switches 55, 55h, 55e and 55d are closed, interlocking the associated tape and camera drive motors, and switch 53 is closed, starting drive motor 59. That drives selsyn generator 58 and the tape and camera motors which are interlocked with it.

Thus all motors are started simultaneously and operate synchronously, whatever the speed of main drive motor 59. The various coordinates of the camera motion, which is originally produced in any arbitrary manner such as by manualand mutually independent operation of hand wheels i), 5Go, and 50c, are then recorded in their respective channels in a definite time relationship.

To reproduce the recorded motion, the record tapes 3G, 35D and 38o are reset in their original positionson'their drums, preferably with the aid of the starting marks, and switches 4G, 55h and licareshifted to repeat position. The film S14 in the camera may be the same lin previously exposed and undeveloped, reset to its original starting position; or may be a fresh film, depending upon the photographic operation involved. With theswitohes in lines 54 closed, switch 53 is closed, againsilnultaneously startingthe camera and the various.recording-repeating channels. f

Thelatter now operate in their repeating function anddrive the camera through thesame kmotions previously arbitrarily imposed.

It is sometimes .useful to record first only one coordinate of camera motion, full attention of the operator Abeing then available for the details of the motion desired (with or without actual exposure of the camera film). That channel can then be set to repeat, thus driving the camera motion in the first coordinate while cameramotion in a second coordinate is introduced man ually and recorded by its channel. Finally, motion in the third coordinate can be recorded while the camera automatically repeats the records from the first two channels. Thus a complete record of the desired motion in all three coordinates is produced without the necessity of handling and coordinating more than one mann ualcontrol ata time. Illustrative procedures employing a recording-repeating system in composite photography are discussed below.

An illustrativeembodiment of a camera mount for carrying outthe invention is shown somewhat schematically in'Figs. 2 5-and 13. The'particula-r embodimentillustrated is based upon an existing nodal point camera mount, designed to provide pan and tilt motions about axes 1 I and 12, respectively, which intersect at the nodal point of the lens I3 of the camera 14 (Fig. 13). Advantages inherent in that location of the axes of camera rotation are discussed, for example, in U. S. Patent No. 1,971,486, issued on August 28, 1934, to H. G. Jennings, and apply with increased force in connection with the present invention. An important characteristic of such a mount is the fact that there is no spurious relative movement at the image plane between images of objects at different distances from the lens.

Camera mount 10 comprises a base 69, adapted by means not shown to be secured to a tripod or other support and having a vertical post '15; a frame casting 1B supported on post 'I5 and rotatable with respect to base 69 about vertical pan axis 'Il on bearings indicated at 'I1 and 18; a cradle 80, having a pair of cylindrically curved rail surfaces 8|, so slidably related to frame 'I6 as to allow relative rotation of the cradle about tilt axis 'l2 (Fig. 13) and a carriage 84, slidably mounted as by ways on cradle 80 and adapted to carry the motion picture camera. 14 with its optical axis 83 parallel to ways 85. Carriage 84 is adjustable along ways 85 by means shown as the rack 8B and the hand-wheel 8l, geared to the rack by gear train 88, so that the nodal point of the camera lens can be set accurately to tilt axis 'l2 for a lens of any focal length and for any focal adjustment of the lens with respect to the camera.

Similaislides can be provided for vertical and lateral adjustment of the lens nodal point, but it is preferred to mount each camera, or each type of camera, on carriage 84 by means of an adapter plater, indicated schematically at 8S, which is so designed as to properly position the camera laterally and vertically with respect to the axes of mount rotation 'H and l2.

The motion of cradle 89 with respect to frame 'i6 is guided by pairs of supporting rollers 80, 9|, which are carried by shafts 92, 93, respectively, journaled in vertical plates9495 of frame 16, and which engage rail surfaces 8l of the cradle; and by hold-down rollers 98, carried by the similarly journaled Shaft 99, which engage an oppositely facing cylindrical surface FIG, coaxial with rail surfaces 3l on the cradle. Rails 8|, |00 are circularly curved about tilt axis l2. The cradle motion (tilt) is driven by a pair of pinions H0 rigidly mounted on shaft Ill, journaled in frame T6, and which engage gear sectors H2, mounted on the cradle coaxially with rails 8| and |00. Pinion shaft lll is driven alternatively manually by handwheel l i3, which is shown mounted directly on the shaft, but can instead be linked to it by a suitable gear train; or by tilt servomotor Ml (corresponding functionally to'motor 28 of Fig. l). The shaft of motor Ml is linked to shaft l i i by a reduction geartrain indicated at l l5. Motor Mi is removably mounted on frame 16, with its shaft and pinion IIE projectingthrough a clearance hole l Il in the frame. Removal is utilized here as a simple equivalent of drivingly disconnecting the motor from the cradle (as by a disconnectible clutch) so that the motor inertia and friction are eliminated when the cradle is moved in tilt by manual or other operation.

The momentary tilt lposition -of the camera. mount is electrically indicated for control purposes by means of three tilt synchro generators, GI, G2 and G3, mounted on subframe vl2l (Figs.

9 4 and 5). The rotor shafts of the generators are driven through suitable gearing from pinion Shaft lll. As illustrated, GI and G3 are connected together at a lzl speed ratio by gears |23 and |24; and G2 is connected to them at a 4:1 speed ratio by pinion E25 on its shaft meshing with gear |25 on the shaft G! Gear |21 on the shaft of G2 meshes directly with gear |28 on pinion shaft i i. Universal connections |2| are indicated in the rotor shafts to insure free operation. The gears E2?, |28 are preferably so proportioned that the full operation range of camera 'tilt motion about tilt axis 'l2 corresponds to 'approximately one revolution of Gl and of G3 'and four revolutions of G2. Generators GI and G2 are then available for a dual speed synchro system (see below) and correspond generallyto synchro 29 (say) of Fig. l; and G3 is available 'as an auxiliary one speed synchro, for use, for example, with a remote hand wheel. Electrical connections from the three generators are "omitted for clarity from Figs. 2 5, but are illustratively shown in Fig. l and described below.

The pan motion of frame 'i6 and of the structure supported thereon is driven with respect to base t9 through a base drive gear 235, fixed on base column l5. A manual drive is provided, comprising a pan handwheel |36 mounted on frame 'l5 and connected as by spiral gears E31 to a jack shaft |38 journaled on frame d6 and carrying gear |323l which meshes directly with base drive gear |35. Rotation of handwheel |36 causes gear |39 to walk around fixed gear |35, carrying frame 'it and the camera with it. A power drive is also provided, comprising pan servomotor Mib (corresponding to motor 28h, say, of Fig. l) which is` detachably mounted on frame 16 with its shaft and pinion |4E) projecting through a clearance hole |4| and connected to pan drive gear |35 by a reduction gear train indicated at |42.

The pan position of the camera mount is electrically indicated for control purposes by a set of three synchro generators Gib, G2?) and G3i), which are mounted on subframe |45, are driven by gearing 545|, and perform with respect to the panrmotion the same functions which generators GI, G2 and G3 perform for the tilt motion. Generators Gib and G31) are connected together at a 1:1 speed ratio by gears le@ and |41, and are driven by gear |48 which meshes directly with, and is the same size as, a pan control gear |49, fixed on base column l5. Generator G2?) is driven directly from fixed gear ILES by a gear 50 whose pitch diameter is one quarter that of gear |49. Thus generator GZlr makes four revolutions, and generators Gib and G3i) make one revolution each, for every 360 of camera pan motion. Pan generators GIb, G2219 and G3b are electrically connected to a pan control channel in the same manner that tilt generators GI, G2 and G3 are connected to the tilt control channel, as shown in Fig. and described below.

Camera mount 10 can be operated manually, like an ordinary nodal point camera mount, by manipulation of hand wheels i i3 and 935. Manual operation can also be handled from a distant location by making use of the servocontrol system, )to be described below, and manipulating handwheels associated with that system. Mount lil is also adapted to be used in conjunction with a recording-repeating mechanism, so that any arbitrary pan and tilt motions can be recorded, and then repeated immediately or at any later time. Y, o o o Translational camera motion although not speciiically included in the illustrative embodiment of Figs. 2-5, can be provided, for example, as shown schematically in Fig. l, or as shown in a more detailed embodiment in connection with Figpl3 (see below).

Figs. 6-9 illustrate a preferred form of a recording repeating mechanism VM, including two channels. Additional channels can be provided as required, for example by duplicating one or both of those shown. Central supporting frame and gear box lfii is mounted on a firm base |8| (which may also support additional units) and carries the various elements of the two recordingrepeating mechanisms symmetrically arranged on its opposite faces. The elements of one channel (A) are shown in Fig. 6 mounted on the front face of frame iti?. Directly behind each of those elements is the corresponding element of the other channel (B), mounted on the rear face of frame i3d. The mechanisms of the two channels are duplicates and will be described by reference to some parts of one and other parts of the other, as conveniently shown in the drawings. Fig. 7 is an end elevation, partially broken away, showing elements of channel A to the left and elements of channel B to the right of frame iti?. iUnnecessary duplication of drawings is avoided in Fig. 7 by breaking away the two channels at different section lines, those lines being indicated in Fig. 6. f

Each recording-repeating channel comprises a tape moving mechanism |15, adapted to move a record tape past the recording or repeating tool, and a recording-repeating head il@ adapted for supporting that tool in engagement with the tape, and for moving the tool transversely of the tape.

The machine illustrated is adapted to use conventional perforated motion picture iilm as record tape. The film |84 is loaded on a supply reel |35, from which it is drawn by a sprocket Hit. (For clarity of illustration the lm is omitted in channel A of Fig. 7 That sprocket is mounted on sprocket shaft |35:` which is journaled in frame it and driven by the selsyn or synchronous motor I8? through a suitable gear train, indicated at |88. Sprocket shaft |89 is common to both the mechanisms A and B; so that both are driven together from the single motor |87, which may thus be considered to correspond to the two motors 32 and 32h (say) of Fig. l. From sprocket |36 nlm |84 passes over and drives a freely revoluble drum and returns to the sprocket. Drum |963, turning on a stub shaft |94 xed in frame Hic, supports the moving nlm in a position which is accurately maintained in both coordinates transverse to the film motion, that is, both radially and axially with respect to the drum. Radial disk |95 is mounted on one face of drum |93 and is urged by springs 92 against one lm edge, pressing the other lm edge into uniform contact with guiding peripheral flange |93 at the opposite drum face. The iilm is guided by suitably placed freely revoluble rollers ii, and is maintained in firm contact with the periphery of drum Hit by a tension roller |97. Roller |97 is mounted on a lever 98, centrally pivoted at |99, and is adjustably urged against the film by tension spring 2Q@ which acts on the opposite end of lever |38 and is adjustable by thumb screw 2M. Film perforations 265 are brought into mesh with sprocket teeth Ziit by conventional sprocket clamps, shown schematically at 2G? and 208 in Fig. 5 only. Film |84 is finally rewound on takeup reel 2H),

gear train |88, record film |84 will then be driven at the same speed as the photographic film in the associated camera, facilitating correlation between the resulting record of camera motion and the film taken by the camera during that motion. As illustrated, a single motor |81 is physically connected, by means of shaft |89, to the film sprockets of two channels. Additional channels can be similarly drivingly connected to the same motor |81, or alternatively, separate motors can be provided for some or all of the channels, as indicated at 32, 32D, etc., in Fig. 1, electrical synchronizing means being then preferably provided.

Recording-repeating head |16 is constructed as a unit which is so mounted on frame |80 as 2 to be located with high accuracy and yet readily demountable. Head case 2|5 is pivoted on stub shaft 2 6 by means of a bracket 2 I1, which is axially confined on the shaft by spring retainer 2|8. frame |36 by set screws 2|9, and projects on opposite sides of the frame to support the heads |16 of both channels A and B. Head case 2|5 is preferably adjustably mounted on bracket 2 |1 for convenient variation of the overhang of the head. As illustrated, inwardly directed flanges 226 on the two arms of bracket 2|1 slide in grooves 22| in the sides of head case 2|5, set screws 222 being tightened on the flanges to lock the head in adjusted position. An adjustable counter-balance is preferably provided, as indicated by the threaded stud projecting from the rear end of case 2|5 and carrying a balancing weight 224.

A recording or a repeating tool 225, according to the process to be carried out, is mounted by means of a thumb screw 226 (Fig. 8) at the free end of an arm 221, which is rigidly clamped to vertical shaft 236, journaled in case 2|5. Tool 225 is located adjacent the peripheral surface of film drum |98 on a radius parallel to the axis of shaft 236, and is movable, by swinging of arm 221 about that axis, transversely across the drum surface and hence across a film |84 running over the drum. 221 is replaced by an arm of different length, the correct location of tool 225 with respect to drum |90 can be maintained by suitable adjustment of the entire head v2|5 with respect to bracket 2|1 as described above. Shaft 238 carries a gear 23| which meshes with pinion 232 on shaft 233. That shaft carries gear 236 which meshes in turn with pinion 231, mounted with gear 239 on shaft 236. Finally, gear 239 is engageable by pinion 24U, mounted on output shaft 24| of a reduction gearing indicated at 242 driven by servomotor M2 (which corresponds to motor 38 of Fig. 1). The motor is so mounted in sleeve 245 that shaft 24| and pinion 240 are eccentric with respect to the sleeve. Rotation of the mounting sleeve in case `2|5 about an axis parallel to shaft 238 brings pinion 246 selectively into and out of mesh with gear 239. A detent device 246 is preferably provided to define two suitable rotational positions of sleeve 245, at

Shaft 2|6 is rigidly mounted in a bo-re in ff;

If for any reason (see below) arm ,L

which the gears are respectively in and out of mesh, and a which motor M2 is accordingly drivingly connected to and disconnected from arm 221. The gear ratio by which servomotor M2 is linked to shaft 230 and hence to arm 221 depends primarily upon the speed and torque characteristics of the motor and the maximum anticipated rate of arm movement.

Two synchro transformers T| and T2 are mounted on the upper face of case 2|5 with their rotor shafts 252 and 253 respectively coaxial with shafts 233 and 238 and linked thereto by universal couplings indicated schematically at 254 and y255. The ratio of gear 23| and pinion 232 is such that the swinging of arm 221 through the angle required to carry tool 225 across the useable portion of film |84 accompanies rotation of shaft 233 through approximately one revolution. The ratio of gear 236 and pinion 231 is such that shaft 238 rotates four times as fast as shaft `233. Thus synchros TI and T2 are available for use in a dual speed synchro system, and together correspond to synchro transformer 36 of Fig. 1.

The entire recording-repeating head |16 may be allowed to swing freely about its supporting shaft 2|6, being so balanced as by adjustable counterbalance 224, that gravity tends to swing it counterclockwise (as seen in Fig. 6) with such a torque as to produce the desired downward force of tool 225 against the surface of record lm |84. For recording, tool 225 is preferably a cutting point of the type ordinarily used for cutting sound records in phonographic recording, and a working force of a few ounces is found to be satiafactory. For following a previously cut record groove, such as is indicated at 228 in Fig. 9, a sapphire phonograph needle is preferably used, and that also operates satisfactorily with a force of a few ounces.

Alternatively, contact between the recording or repeating tool 225 and lm |84 may be positively established by anchoring head |16 at a suitable rotational position about shaft 2|6. Such a positive anchor is preferably used during recording to insure a record groove of uniform depth; and the head is preferably allowed to float, as described in the preceding paragraph, during repeating. This is accomplished in the present instrument by a spring latch 260, which is mounted on stud 26| on frame |80 and may be swung about that stud into inoperative position, indicated by dot-dash lines in Fig. 6, when head |16 is to be operated under gravity, as just described. When latch 260 is in operating position, as shown in solid lines in the drawings, the slot 259 at the end of finger 265, extending rigidly from head oase 2|5, receives vertical rod 262 of the latch assembly (the length of the slotl accommodating longitudinal adjustment of case 2|5 on bracket 2|1). Rod 262 is threadedly mounted, as indicated at 268, in latch base 263 and carries a defining flange 264 adapted to engage and support the lower surface of finger 265 at a level which is adjustable by screwing rod 262 into or out of base 263. A lock nut 264:1l is provided to lock rod `262 in its adjusted position. Cap 266 is carried by the upper end of rod 262 and is urged downwardly on the rod by compression spring 261 against the upper surface of finger 265, thus normally urging that nger into engagement with defining flange 264. That engagement is yieldable by compression of spring 261, but is positive, so fas as normal action of recording or repeating tool 225 is concerned, if

the spring is relatively stiff. The level of tool 225 with respect to record nlm 184 is then determined by the adjustable level of flange 264. Lift lever `21D is pivoted at 211 on the side of latch base 263, and has a camming surface 212 which is so formed that, when the lift lever is rotated clockwise as seen in Fig. 7 (or counterclockwise as seen in Fig. 8A), cam surface 212 engages nger 265 and lifts and supports it, compressing spring 261. Tool 225 is thus raised from its operating position free of drum 190 and record lm 184.

Fig. l0 illustrates schematically a preferred arrangement of electrical circuitry for combined operation or the recording-repeating unit 114 of Figs. 6-9 with the camera mount 1li of Figs. 2 5. Provision is also shown for connecting other apparatus in place of the camera mount (see below). For the salie of clarity, only one channel of the control system, controlling for example, the tilt motion of the camera and utilizing one channel of dual recording-repeating unit H4, is included in Fig. l0. It is understood that a complete control system ordinarily includes one or more additional channels of similar or identical design, controlling motion in whatever other coordinates may be involved in a particular setup. Such a combination of channels operating in association is illustrated functionally in Fig. 1.

One-speed synchro generators G1 and G3 and four-speed generator G2, the mechanical mounting and motion of which have already been described (Figs. 4 and 5), are electrically connected as illustrated in Fig. l0. The rotors 4 of all three synchro generators are connected in parallel via lines 3&1 and 332 to a suitable source of alternating current, typically shown as 2G volts, 40G cycles. rl'he three stator windings of oneand l-speed generators Gl and G2 are connected respectively by lines 303 and 33e to the corresponding windings of one and l-speed synchro transformers T i and T2, which are mounted as already described on recordingrepeating head 116. The three stator windings of generator G3 are connected via lines 305 to contacts 1, 2 and 3, respectively, of an electrical connector S i, by means of which a synchro transformer T3, driven by a hand wheel 33@ or other control device, can be connected for the purpose of controlling the camera motion while a record of the motion is made (see below). Such a control then replaces the hand wheel on the camera mount, and has the advantage that it can be operated remotely.

lf the position of the rotor of synchro transformer T1 does not correspond to that of generator G1, an A. C. error signal is generated in rotor d of Tl, the phase of the signal. corresponding to the sign of the error; similarly, an error signal is generated in the rotor oi 4-speed synchro transformer T2 whenever its position does not correspond to that of -speed generator G2. For small errors the error signal from Ll-speed transformer T2 is about four times as large as that from one-speed transformer T1, and use of the e-speed signal in the servo system leads to correspondingly greater accuracy. On the other hand, when the error is large the phase position of the rotor in the l-speed transformer doe-s not necessarily represent correctly the phase sector of the error. Under such conditions (and also when apparatus not equipped with a fl-speed servo is used with the recorder-repeater, as will be described) control is switched from the 4-speed to the one-speed synchros. Such switching is accomplished automatically in the present system by voltage sensitive relay H whenever the error exceeds some predetermined value less than that a-t which the mount will shift phase sector; and can also be accomplished manually when desired by shifting speed switch E.

vShe individual switch arms and terminals of each switch in the present system are designated by numerals written as suiiixes to the letter by which the switch itself is designated. However, for clarity in the drawings only the numerals are shown for the arms and terminals, the switch letter being written once for each switch assembly.

When speed switch E is at dual speed position (as shown) and relay H is deenergized (as shown) the error signal from the rotor of 4-speed synchro transformer T2 is transmitted via lines 316 to relay switch terminals H2 and H5, through switch arms H1 and H4, Via lines 311 to switch terminals E3 and E11, and through switch arms El and E16 to lines 312. The one-speed error signal from transformer1 T1 is transmitted via lines 315 to switch arms El and Eli, through those switch arms to terminals E2 and E5 and Via lines 316 to relay switch terminals H3 and H6, which are open. Lines 3i5 are also connected across the relay coil H1 of A. C. voltage sensitive relay H. Hence when the one-speed error signal exceeds the value at which relay H respends, the relay is actuated. That opens the 4-speed error circuit at relay switch terminals H2 and H5, and connects instead the one-speed error signal, which is then. transmitted from terminals H3 and H5 through relay H, lines 311 and switch arms E1 and E10 to lines 312. As soon as the one speed error signal has been sufciently reduced, for example by action of the r servo system, relay H is again deenergized and drops -to its ll-speed position, again connecting the l-speed error signal to lines 312 by the circuits already described.

If switch E is shifted manually to single speed position, switch arms E1 and E12 open the described connection oi lines 352 to relay H and connect them instead via switch terminals E9 and E12 and jumpers 318 to switch terminals E3 and E5. The shifting of switch arms E1 and Ell opens the described connection between onespeed transformer T1 and relay thus removing the small load that relay coil H1 imposed upon the transformer; and connects the transformer T1 instead to switch terminals E3 and E6, and hence to lines 312. Thus switch E in single position takes control completely away from relay H, disconnects the relay coil H1 and connects the one-speed error signal to lines 312.

The primary function of record-repeat switch F is to deliver the error signal from lines 312, connected to switch terminals Fl and Fri, selectively to recording servo amplifier 32d during recording (via switch arms F1 and F4 and lines 321) or to the camera servo amplifier 322, which controls the camera position, during repeating. Ampliliers 32B and 322 are phase sensitive, receiving power via lines 323 from a suitable A. C. source which is in phase and preferably identical with that supplying lines 301 and 322. Lines 325 from the input of camera servo amplifier 322 may, under certain conditions, lead directly to switch contacts F3 and F6 (in contrast to the arrangement of Fig. l0), and in that case shifting of switch F to repeat position will deliver the synchro error signal from lines 312 through 15 switcharms F1 and F4 directly to lines 325 and hence'tozcamera ampliiier 322.

Amplifier 322 corresponds generally to repeating ampliiier 43 of Fig. l, but performs also a second function. It is convenient when recording the vcamera position and hence when the synchro error signal in lines 352 is being delivered to recording amplifier 328 and thus controls the position of the recording tool, to provide automatically some external control signal to the input of camera servo ampliiier 322. That signal (coming in the present instance from hand wheel synchro transformer T3) may then be used to control,.or in effect to drive, the camera motion, either from a location remote from the camera, or :directly from the camera but without the necessity of providing manually the actual drivingtorque. (Alternatively, the camera motion may be driven by a. conventional hand-wheel mechanically linked to the gear train of the camera drive as already described.) Means are also provided, including switch J and switch arms F13 and F16 of switch F, for connecting in place of camera servo ampliiier 322 the corresponding element of other apparatus, which may be of another type. rl-he detailed functioning of switch J and of switch arms VF13 and Fifi of record-repeat switch F, which are associated with connector S3, will be described later. When the camera is to be controlled (for recording or repeating) through camera amplifier 322, switch J is kept in camera position, as shown.

With the arrangement illustrated, lines 325 from the input of camera ampliier 322 connect through switch J in its camera position and via lines 326 to switch arms F1 and Fli! of recordrepeat switch F. When that switch is in record position, as shown, the switch arms F1 and F10 connect through terminals F8 and F11 and lines 321 to contacts d and 5 of connector S1 and through the mating connector S2 to the rotor 4 of hand wheel synchro transformer T3. The error signal from T3 is thus delivered to amplifier 322 and controls camera servomotor M1 (see below), causing the camera mount to follow whatever motion is fed to synchro T3 by hand wheel 338.

When switch F is shifted to repeat position, the described circuit from the rotor of synchro T3 to camera ampliiier 322 is opened at switch terminals F8 and F11. and the ampliiier is connected instead via terminals F9 and F12, jumpers 332,*switch terminals F3 and F5, and switch arms F1 and Fd to lines 312, and thence by the circuits already described to the rotor of one or other of synchros T1 and T2 on recording-repeating head i115. Camera servomotor Mi causes the camera to follow the motion of arm 221, which is guided by whatever record film 184 is in the machine 114. The input circuit to recording servo amplifier 321] is opened at switch terminals F2 and F5 during the repeating cycle, and servomotor M2 in recording-repeating head 111e` is preferably disconnected from arm 221 in the manner already described (Fig. S).

Camera servo amplifier 322 may be so constructed as to drive directly a suitable servomotor M1 on the camera mount. However, in the illustrative embodiment of Fig. 10 further amplification of a non-electronic type is provided by an amplidyne generator, shown schematically at 333. The output from ampliiier 322 is transmitted via lines 33i to the eld coils 332 of generator 333, which is driven continuously by a motor 334. One generatorarmature winding is short circuited, as indicated, and 'carries a relatively large current whichiinduces in a second winding a voltage approximately proportional to the controlling current in field coils 332. That voltage, after commutation is applied as a direct current voltage avia lines'331 to the armature of D. C. servornotor ."M1. 'The eld of motor M1 is excited via lines 338 byan outside source of direct current, which may also power amplidyne motor 334 as illustrated. The lines 331 are tapped via lines 39.3 to feed the amplidyne output voltage back to servo amplifier 322, where it is applied in the usual way as feed back to obtain improved operating characteristics of the system as a whole.

In summary of Fig. l0, servomotor M! applies to the camera mount a torque of appropriate sign and magnitude to reduce any position error that exists between the synchro transformer T1, T2 or T3 (whichever is connected by the described switch system to servo amplifier 322) and the corresponding synchro generator G1, G2 or G3 on the camera mount. The camera motion therefore substantially duplicates that of the controlling synchro transformer. That controlling transformer during a. recording cycle is typically hand wheel synchro T3; and during a repeating cycle is one or other of recording-repeating head synchros T1 and T2, depending upon the size of the position error (which controls relay switch H) and upon the position of switch E. rfhus during recording, with switch F at record the camera motion follows hand wheel synchro T3 or its equivalent and arm 221 on the recording head follows the camera motion. During repeating, with switch F at repeat, arm 221 follows the previously prepared record groove 228, and the camera motion follows arm 221.

During normal operation of the record-repeat unit with the camera mount here described, or with any mechanism similarly equipped with both oneand 4-speed synchros, greater accuracy is ordinarily achieved with switch E at duaL as illustrated, so that the system operates normally on the 4-speed synchros. rl'he error signal ordinarily is large enough to actuate relay H only when the system is rst connected or is under some abnormal condition. Under such conditions, it may be convenient to throw switch E t0 single, and that is done also when the recordrepeat device is to be used with apparatus having only a one-speed synchro system (see below).

rlhe apparatus shown in Fig. l0 represents a typical embodiment of circuitry associated with one channel of a recording-repeating system, adapted to handle camera motion in one coordinate. By dupicating such equipment to any required extent, additional components of camera motion can be handled in the same manner, one channel preferably being available for cach component.

rThe apparatus already described, including the camera mount 10 of Figs. 2 5 and the recorderrepeater 114 of Figs. 6-10, illustrates one manner of controlling and repeating camera-subject motion, namely by moving the camera with relation to its support vand by recording and repeating that motion. Under certain conditions it is preferable to obtain the camera-subject motion by moving the subject as a whole and holding the camera xed. Figs. 11-13 illustrate schematically a preferred illustrative manner of producing such motion of the subject, the subject itself being typically shown as the easel 3BE! (Fig. 12) on which a painting, photograph and the like can be mounted and photographed by a camera 361. Easel 360 can be replaced by a three dimensional subject, for example a miniature model of a scene, and is to be considered as a schematic representation of any type of movable subject. The camera is shown mounted on a rigid stand 362 on the floor 364, and having its lens axis 363 horizontal, but may be movably supported, as on a mount such as 19 in Figs. 2-5.

As illustrated, easel 363 is capable of independent motions of translation along three rectangular coordinates, which will be designated respectively as transverse (of camera axis), vertical and longitudinal (along camera axis). The easel proper is suspended by a rigid frame 365, which may itself be adjustable, from an assembly 356 of carriages which are relatively movable in translation. Frame 365 is directly connected to transverse carriage 310, which is mounted as by rollers 31| for free translation with respect to a second or vertical carriage 314 in a horizontal direction parallel to the easel surface and normal to the axis 333 of the camera lens as illustrated. Vertical carriage 314 is vertically movable in translation, guided as by rollers 315 with respect to main carriage 318, and carries transverse carriage 319 and easel 339 along with it in that motion. The total weight cf carriages 314 and 319 is preferably approximately balanced, as by a counterbalance 316 connected to carriage 314 by cable 311, which passes over pulleys 319 mounted on main carriage 318. Finally, main carriage 318 is supported on one or more fixed overhead beams 380 by rollers 38|, which permit longitudinal motion of the three carriages as a unit in a direction parallel to lens axis 363, n

While the illustrated suspension of easel363 from overhead beams has been found very convenient, a similar result can be obtained by a system of carriages supported in other ways. It is to be understood that the three motions of translation illustrated can be replaced or supplemented to any desired extent by other types of motion, including rotation or curved lines of motion about any selected centers, the present easel ysupport with controlled motion in three rectangular coordinates being illustrative.

A typical form of power drive is illustrated for driving each of the easel motions. This will kbe described in detail as applied to the longitudinal `motion of main carriage 318, the other two motions being driven in a similar manner. An effectively endless cable 385 passes over two idler pulleys 386, main carriage 318 being connected to one pass of the cable as at 381. Cable 385 also passes around a driving drum 388 which is fixed with gear 389 on a shaft 399, journaled in a suitable xed mounting plate 39|. A hydraulic motor 394, also mounted on plate 39|, is drivingly coupled to gear 389 lby a gear train designated generally by the numeral 338. Thus rotation of motor 394 moves cable 385 over pulleys 386 and draws carriage 318 along beam 339 in one direction or the other. Hydraulic motor 394 preferably comprises what is commonly known as the B-end of a hydraulic torque amplifier of a type which isl available commercially. The overall rfunction of the hydraulic torque amplier is to translate a relatively small D. C. electrical control signal,.ap plied via cable 485, into the relatively large torque output of hydraulic motor 394, the direction and magnitude of that torque being controlled by the ysign and voltage of the control signal. Hydraulic motor 394 is driven by iiuid circulatedv through lines 499 and 409 from a constantly driven hydraulic pump, or A-end, 401, the output of vwhich 13 is variable as to both rate and direction of iiow and is controlled via a hydraulic preamplifying mechanism 496 in response to the electrical control signal from cable 495. That control signal may be obtained in any suitable manner, but is supplied in the present preferred embodiment of the invention as the output from an electronic hydraulic unit amplifier 4|5 (Fig. ll), the input signal to that amplier being produced as will be described. The longitudinal drive system, as so far described, may be considered as an illustrative means of driving the relatively heavy load of carriage 318 in one direction or the other in response to a positive or negative direct current signal of relatively low amplitude, supplied as output voltage from amplifier 4 5.

A pair of synchro generators G1 and G8 are mounted on plate 39| (G8 being directly behind Gi in Fig. 12) with their rotors driven together as by gear 4I5 which meshes with the gear train 398 through which cable drum 389 is driven. Generators G1 and G8 are thus driven in rotation in accordance with any motion in translation of carriage 318, and have a deiinite rotational position corresponding to every translational position of the carriage. The overall gear ratio Abetween gear 389 and synchros G1 and G8 is preferably such that motion of carriage 318 throughout its available range of longitudinal motion corresponds to somewhat less than one complete rotation of the synchros,

The preceding description of the operating mechanism for the longitudinal motion of carriage 318 is applicable also to the vertical operating mechanism of carriage 314 and to the transverse operating mechanism of carriage 310, shown in Fig. l2, provided certain modifications are made, including obvious changes in terminology corresponding to the superficial structural differences, addition of suiiixes -b and -c respectively to identifying numerals, and substitution of G9, Gill and GI l, GIZ respectively for G1, G8. Motion in each of the three coordinates is thus under control of an electrical voltage, supplied, by means to be described, to the corresponding hydraulic preamplifier 406, 496D or 406e via cable 495, 405b or 495e. And the momentary positions of the carriages, and hence of easel 350, in each of the three coordinates is represented or indicated by the rotary positions of a corresponding pair of synchro generators, G1, G8; G9, GIU; or GI I, GIZ.

Electrical control apparatus for conveniently providing and controlling the voltage to be supplied to hydraulic preampliiers 496, 40Gb and 408e to produce the desired components of motion of easel 360 is illustrated in Fig. 11. That figure shows only one channel of the control apparatus, namely, that controlling longitudinal easel motion, it being understood that other similar or identical channels are to be provided, as indicated in Fig. l. The apparatus of Fig. l1, with the exception of the parts already described and shown in Fig. 12, is preferably mounted in a cabinet or control console, such as is illustrated at 430 (Fig. 12), with the various dials, switches, etc., to be described, arranged on one of the three panels of that console, say 43|. Panels 43|b and 43|c similarly accommodate the corresponding controls associated with the other two control channels.

n An important feature of the easel control system of Figs. l1 and 12 is the provision in control console 430 of an indicator and control element associated with each component of easel motion,

and representing by its position the position of the easel in the associated coordinate. The longitudinal motion indicator and control element comprises the shaft 434 (Fig. l1), which carries directly position dial 436 and is preferably linked as by a suitable gear train indicated schematically at 434, to Vernier dial 431, the latter rotating preferably ten times as fast as dial 436. Suitable scales 436e and 431a are carried by dials 436 and 431, respectively, to indicate to the operator the momentary longitudinal position of easel 360. Indicator shaft 435 is linked to the longitudinal easel motion, in the present preferred form of the invention, by an indicator servo system. That servo system includes synchro generator G1, linked as already described to the longitudinal motion of carriage assembly 366 along beam 380; synchro transformer T1, mounted in console 430 and connected to shaft 435 for rotation therewith; servomotor M4, drivingly connected to shaft 435; and servo amplifier 440. The three stator windings of generator G1 are electrically connected by lines 441 to the corresponding stator windings of transformer T1. The rotors 4 of generators G1 and G8 are connected in parallel by lines 442 to a source of alternating current, shown typically as 26 volts, 440 cycles. The rotor of transformer T1 is connected via lines 444 to relay switch arms K4 and K1, and through those arms either to contacts K5 and K8, when relay K is deenergized as shown, or to contacts K6 and K9, when relay K is energized as during normal operation (see below). The latter contacts, K6 and K9, are connected via lines 445 to the input of servo amplifier 440, in which the error signal from T1 is amplified and rectified with phase discrimination. The amplifier output is supplied over lines 446 to the field coils of servomotor M4. When relay K is energized, the error signal from the rotor of generator T1, which is zero only if the rotational position of shaft 435 corresponds to the momentary longitudinal position of easel 360, is supplied to amplifier' 440, and after amplication and phase sensitive rectification drives motor M4 in such a direction as to reduce the error signal. Thus shaft 435 in effect follows the longitudinal position of the easel, maintaining the one to one correspondence defined by zero error signal. Dials 436 and 431 are calibrated in accordance with that correspondence. Shaft 435, like generators G1 and G8 makes less than a completes revolution for the full range of easel movement.

The control function of shaft 435 in the present embodiment of the invention is performed by actuation of switches U and V at independently predetermined rotational position of the shaft. That actuation is typically accomplished, through physical connections that are indicated by dashed lines in Fig. 11, by cams 450 and 45| respectively, mounted on cam arms 452 and 453 which are frictionally mounted on shaft 435 for independent rotational adjustment with respect to the shaft. Adjustment of cams 450 and 45| is facilitated by providing on cam arms 452 and 453 scales or pointers such as are indicated at 454 and 455, by which the position of switch actuation can be read with relation to dial 436, and hence with relation to the longitudinal position of easel 360. Switches U and V are shown in Fig. l1 in their normal, or unactuated, positions. As each cam 450, 451 approaches its predetermined rotational actuating position it shifts the associated switch to the right in the drawing into actuated position; and upon reversal allows the switch to drop back to normal position.

In general, switch U acts as a limit switch, the setting of its actuating cam 450 determining the point of the motion of easel 360 inward toward camera 351 at which the eased motion is automatically either stopped or reversed, selection of one or other of these actions being determined by the position of switch R. Similarly, switch V acts as a limit switch on the outward motion of the easel, the setting of its cam 451 determining the position at which outward easel motion is either stopped or automatically reversed. In addition to the automatic stopping or reversing action just indicated, the system can be started or stopped manually by means of switch Q, or by closing or opening master switch P, which controls simultaneously the longitudinal channel and also the other two channels of the easel motion. Momentary operation of push button switch N, either prior to starting of the system by switch Q or P, or while the system is ruiming, manually controls the direction of easel motion, that direction being in if in button N1 is pressed and out if out button N4 is pressed, independently of the previous running direction. Thus switch N serves both as a manual reversing switch and as a means for predetermining direction before operation of starting switch Q or P. The detailed circuitry by which the described functions are carried out will be described presently.

The rate and direction of longitudinal motion of easel 360 is determined as already stated, by the sign and magnitude, respectively, of the output voltage supplied from hydraulic unit amplifier 415 to solenoid 404 in pre-amplifier 406. According to the present invention, that speed controlling amplifier output from 415 is determined in voltage and sign by the amplitude and phase of an alternating input voltage supplied to phase sensitive amplifier 415 over lines 460, 461 and generated in speed voltage generator unit 462. The latter operates on the same basic principle as the error signal generator ordinarily used in a servo system, for example synchro generator G1 and synchro transformer T1. The overall function of speed generator unit 462 is to supply the phase-sensitive rectifying amplifier 415 with either of two alternating current signals which are mutually out of phase and whose amplitude is manually adjustable. Amplifier 415, phase sensitive and reetifying, then translates the received signal into an amplified direct current voltage of a sign dependent on which signal is supplied, and of a voltage dependent on the manually controlled amplitude of that signal.

In Fig. 11 the apparatus of generator unit 462 is diagrammatically enclosed by the broken enclosure line designated 462. The rotor of a synchro generator G13 is locked in a definite rotational position, and is supplied with alternating current over lines 465 from the same source as that which supplies alternating current via lines 442 to hydraulic unit amplifier 415. The stator coils of generator G13 are connected va lines 466 to the corresponding coils of synchro transformer T14, and also to the stator coils of transformer T13 in transposed arrangement as indicated in Fig. 11. The rotors of transformers T13 and T14 are mechanically linked, as indicated by dashed lines, to dials 410 and 411 respectively, by which their rotational positions can be manually adjusted, and on which suitably calibrated scales are preferably provided to indicate the rate of easel travel corresponding to various dial `the output voltages from amplifier 4I5, corresponding to the signals from the two transformers, will normally be of opposite sign, and will drive easel 360 in opposite directions, the speed of easel travel in the two directions being directly controllable by the respective settings of dials 418 and 41 I.

- One or other of the signals from the rotors of transformers TI3 and T|4 is delivered selectively to the input leads 468, 46| of amplifier 4I5, depending upon the condition of relay switch L. Line 412, with its various branches, connects one terminal of each transformer rotor to switch terminal K8, to terminal 1 of connector S4, and also to switch terminal W which isnormally connected by switch arm W4 to amplier input (The function of switch W will be described below in connection with connector S4, with which it is associated. Under certain conditions, for example when connector S4 is. not required, switch W may be omitted, amplifier input lines 468 and 46| being connected directly to lines 418 and 412, respectively.) The other terminals of the rotors of transformers GIB and G|4 are connected, respectively, via line 413 to .relay switch terminal L3, and via line 414 to ter- ,K is energized, switch arm KI connects via terminal K3 to line 418 and thereby to terminal 6 of connector S4 and also to switch contact W2,

'which is normally connected via switch arm WI to amplifier input 468. Y

When relay K is deenergized as shown, the circuit just described is opened at relay terminal K3, so that the speed controlling signals yfrom the rotors of transformers TI3 and TI4 are not utilized. Instead, the input to amplifler 4I5 .is supplied from the rotor of indicator and control transformer T1 via lines 444 to relay switch varms K4 and K1, through those switch arms to lines 418 and 412 respectively, and thence through the two arms of switch W, in its normal position, to input leads 460 and 46|.

vThe effect of supplying amplier 4| 5 with a vsignal from transformer T1 is to confine the easel mount, so far as its longitudinal motion is concerned, in the position corresponding to the vmomentary position of synchro transformer T1 `and of shaft 435 which is linked to it. The latl.ter position remains fixed, once relay K is deenergized, since the input to servo amplifier 440 from transformer T1 is thereby opened at relay kswitch terminals K6 and K9, and the amplifier isso balanced that the output to motor M4 is then insufficient to drive it. But, as already explained, transformer T1 during normal operation (relay K energized) is driven by motor M4 transferring control/kof hydraulic unit ramplifier 22 4I5 from speed control synchro TIB or T14 `to synchro T1, as when relay K is deenergized, is to lock or stow the easel system in its momentary (longitudinal) position. Energization of relay K, on the other hand, puts the easel under control of either the in speed control voltage generated by synchro transformer TI3, or the fout voltage generated by TI4. Relay L determines which of those voltages takes control, and hence in general whether the easel moves in or out.

Relays K and L are controlled by switch means which, `in the present illustrative embodiment, include manual switches N, P, Q, and R, and cam actuated switches U and'V. One side of a power source, which is here illustrated as volts, 60 cycles, but may be any suitable source of direct or alternating current, is connected via line 480 to terminals KIU and LIU, on one side of the coils of relays K and L, respectively, The other side of the power source is connected via line 48| and its branches to switch terminal N2, to switch arm L4, to switch arm RI and to switch arm V4. The relay energizing circuit of relay K extends from its other coil terminal KII via line 483 to switch arm PI of master switch P, and, when that switch is shifted to on position, through terminal P2 and lines 484 and 485'respectively to switch arm QI and terminal Q5. Thence connection may be completed to line 486 either via switch terminal Q3 by shifting switch arm QI to start position, or through terminal Q6 by momentarily pressing push button Q4 toy closed position. From line 486 the circuit'is completed through switch terminal R2 and switch arm RI to power line 48| when switch R is in automatic reverse position as shown. Under that condition, relay K is energized by closing both master switch P and either the toggle QI or push button Q4 of pane1 switch Q; and is deenergized only by opening the master or panel switch.

When switch R is shifted to automatic stop position, the circuit just described is opened at terminal R2.

The energizing circuit of relay K then leads from line 486 through switches V and U in series, passing through switch arm VI to rline 481 and thence through switch arm UI and camera) or switch V` (which is set to occur at the desired limit of easel motion toward the camera). In either instance, or if the circuit is opened at switch P or Q, deenergization of relay K stows the mount in the sense already described.

The energization of relay L is independent of switches P and Q. It is generally controllable .by momentary actuation of either the inor the out button of switch N, and when switch vR is in automatic reverse position it is also controllable by cam actuation of switch U or V. -If

,relay L is deenergized, it can be energized man- ,ually by pressing in button NI, thus complet- Aing an initial energizing circuit from relay coil terminal LII via line 498, across normally connected switch contacts N6 and N5, and through depressed switch bar NI to power line 48|. When .switch RA is in automatic reverse position. relay L is energized also at the set outer limit of easel Amotion by cam actuation of switch U, which `closes' a circuit from relay coil terminal LII amate through. line 491|', switch. arm-v lined and When relay L hasbeen= momentarilyaenergized through.eitherofl theA circuits justA described', a

holding-circuitisnormally'established fromzrelay coiltterminal LH via line 495 toswitch terminal 'L19 and through switchar-mLli, nowtin. energized position, to line` 495.v From:.line= 4QF-.tha circuit passes:through.switch terminals N1 andaNa', nor- `-mallyv connected by. push buttoniNlt', andfviadine 491 to switch terminal V5, which is normally .connected to switch. arm' V4: andi powerA lineK 48 l .'Ilhat. holding circuit is: maintained until .either outx button; N4@ is momentarily pressed orcam switch: Vr isv opened? at the setinner llimitl of.` easel motion. Then relay. his; deenergizedf and*- drops back: to; out position.

Pilot lights: 500i and 50 l: indicate the condition of-energizatiom ofrelay L'. They are connected on. one side to power.v line 480Y and on. the other sid'e via lines` 5il2iand: 50K, respectively; to relay switch terminals. L61. and L5. When. relay. Lis deenergized switch arm 1.4il connects power line 4$1h to; terminal L5, lighting outpilot light50l andi indicating. that; the. easel is ready:- to be started; orJ is actually. moving, out;r and when .relay-f1', is. energized, switch arm. L4. opens. the circuit to; lamp; 50i: andi connects. in pilot light 50B indicating readiness of the system forinward easel: motion..

In` operation, the; followingl settings. are crdinarilylmadebefore the motion isvactually started. Either in button Nif' or out button N4 is momentarily pressed to'determine the direction 'ofi initialmotion, energizing. or deenergizing, respectively, relay L. If.' the easel is-.tomove to a certainlimiti position and then stop, switchl R .isset to"st'op. If the-easelis to-reverse auto- 'matically after. reaching. alimit position, and

move in the oppositeldirection, switch R. is set to reverse Carn1levers,452 and.' l453i are set with reference to dial 436 to the outer and inner limits ofi motion, respectively, at which actuation of switches Uv and V is to limit the motion, stoppinglor'reversing it. Speed dials 41() and 4'I'I'are sett to the speed at which the easel' is to move inward and outward, respectively, determining the amplitude of speed; signals generated by synchro transformers TI3 and.v TM'. In practice, similar adjustments are ordinarily made in the control channels for all. three components of easelzmoticn, the adjustments in each channel beingindependent ofthe others.

If; motion; in two or more` components is to start, simultaneously, panel switches Q are closed in advance in those channels, and the motion is 'started by closing master switch P'. That enerplifier. 415 with the predetermined speed signal from its respective T|3 or TI4, starting the easel motion. Motion in other coordinates, not initially-V started, can be introduced as required at any time by closing switchesQ in the'- corresponding channels. When any one of the motions reaches a preset limit, switch U or V is cam actuated, either stopping the motion by deenergizing relay K (if switch R is at stop), or reversing thedirection of motion by shifting the 'condition of energization of relay L (ifswitch R is at"reverse-). In the latter instance the speed in the/reversed direction is determined by the setting of thev corresponding synchro TIS or TM and is thus independent ofi the speedin the initial direction. The direction of' motion in one or more coordinates .can 'be manually. reversedi at any timeY by.l momentarily: pressingitheaappropriate but-toni of; switch: N.v in; the corresponding channel. 'Dnatareverses the condition-ofirelay. L eitherfby closing the; described initial energizing oircuit'between terminals .Nt and N3 on hyo'pening- .the described; holding circuitbetweennterminals: N1 and; Nt; shifting.l control. :from one ci.A synchros: TIK and. TM. to" the other.. The reversed motion. then. normally continues: until modiediby switonU on V; atthepresetdimit'for motion-a in that. direction. The: motiontcanmbe stoppedV manually ati any timer eithernin. all. coordinates atzonce by: opening.' master.- switchP; orvinrany.:selected` coordinates by opening. panel switches: Q1. inrthe. corresponding. channels. That deenergizes relays K in those channels, `taking control away Afrom Vthe' speed controlvoltage from synchro T la' on Tl 4 2 and substituting.y the stowng signal from synchro= TL Push-` button .Q4 lof panel switch Q is useful for moving-.thee caser a short'. distance, as' in: setting it` accuratelydn a desirediposit-ion.l

Thefoperaticn. of the' easelfmounti drive system as.; soz far described is suiliciently.- accurata and reproducible that it: can. be usedl asa"v repeating systemr underA many conditions encountered in practicez A. sequence'- or motion, automatically performed by.- the A described` controls,` can be repeatedwith. .goodf accuracy. either immediately or at some" later time byxadjusting'the controls to theisamesettingszand allowing them44 to .prform again the sameicontrol operations. However; since errors: of. ratet setting, for example, tend to: be cumulative` in such a system, far greater accuracyfis .attainable when arecordingrepeating mechanism; such'as that alreadydescribed", is used' in. conjunction with the easel mount drive.

Beforel describing that; procedure in. detail; it shouldibemoted that: the easelmountf dri-ve; as showrnin Eiga ll; isladaptedfonmanual' control, say bylaw handwheel) as'4 an alternativeto the speedfiand:llmiticontrols described. In'ltheilbngitudinal channel; forfexample, synchrovgenerator G8 is available for that purpose,- linkled, asindicated; likegeneratorfl?toA the 'longitudinal easel position. The'rotorfo'tf generatorx G8 i'sconnected across alternating currentlrpower lines M2, and its staton windings: are; brought outA Vialinesl 510 tir-terminals ii ZlandSfIof connector S4; Terminais y4'. and 5` offconnectory.Ew are'com'ieetedI respectively yto-inpiit lines 460 and l 4611' to hydraulic unit'- amplifier 441 5, and? connector terminals -Ga'nd 1 are:connected-respectively 'tolines All@k andt 412, Whichare normallyI connected"y to those v input lines byswitch W. Tocpe'ratethe easel by a handwheel, such: asi handwhe'el 31W4 in- Fig. l0. which is- 1mechanically,` connected to` synchro transformer-- T3; switch- W is opened4v` and'i handwheel electriealf'connector- S2j (Fig. l0)v isV plugged into -conneetor-S4 'in F'ig. 1'1. Correspond-ing -f stator' windings oi'feasel-` generator G82 andl handwheel transformer# T3z areA thus connected "tcg'etlier viaAv connector terminals l, 2', and 3, and the transformer `errorsignal;,indicatingV any lack 'of correspondencebetween `the handwheel posi- Athusl causing'- easel"A to follow any 4motion imposedlmanuallyupon handwheel 33 0; With that arrangement terminals E' and T of connector S4 

